/*
 * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under both the BSD-style license (found in the
 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
 * in the COPYING file in the root directory of this source tree).
 * You may select, at your option, one of the above-listed licenses.
 */

#include "zstd_compress_internal.h"
#include "zstd_fast.h"

void ZSTD_fillHashTable(ZSTD_matchState_t* ms, void const* end, ZSTD_dictTableLoadMethod_e dtlm)
{
  const ZSTD_compressionParameters* const cParams = &ms->cParams;
  U32* const hashTable = ms->hashTable;
  U32 const hBits = cParams->hashLog;
  U32 const mls = cParams->minMatch;
  const BYTE* const base = ms->window.base;
  const BYTE* ip = base + ms->nextToUpdate;
  const BYTE* const iend = ((const BYTE*)end) - HASH_READ_SIZE;
  const U32 fastHashFillStep = 3;

  /* Always insert every fastHashFillStep position into the hash table.
   * Insert the other positions if their hash entry is empty.
   */
  for (; ip + fastHashFillStep < iend + 2; ip += fastHashFillStep) {
    U32 const current = (U32)(ip - base);
    size_t const hash0 = ZSTD_hashPtr(ip, hBits, mls);
    hashTable[hash0] = current;
    if (dtlm == ZSTD_dtlm_fast)
      continue;
    /* Only load extra positions for ZSTD_dtlm_full */
    {
      U32 p;
      for (p = 1; p < fastHashFillStep; ++p) {
        size_t const hash = ZSTD_hashPtr(ip + p, hBits, mls);
        if (hashTable[hash] == 0) { /* not yet filled */
          hashTable[hash] = current + p;
        }
      }
    }
  }
}

FORCE_INLINE_TEMPLATE
size_t ZSTD_compressBlock_fast_generic(ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
    void const* src, size_t srcSize, U32 const mls, ZSTD_dictMode_e const dictMode)
{
  const ZSTD_compressionParameters* const cParams = &ms->cParams;
  U32* const hashTable = ms->hashTable;
  U32 const hlog = cParams->hashLog;
  /* support stepSize of 0 */
  U32 const stepSize = cParams->targetLength + !(cParams->targetLength);
  const BYTE* const base = ms->window.base;
  const BYTE* const istart = (const BYTE*)src;
  const BYTE* ip = istart;
  const BYTE* anchor = istart;
  const U32 prefixStartIndex = ms->window.dictLimit;
  const BYTE* const prefixStart = base + prefixStartIndex;
  const BYTE* const iend = istart + srcSize;
  const BYTE* const ilimit = iend - HASH_READ_SIZE;
  U32 offset_1 = rep[0], offset_2 = rep[1];
  U32 offsetSaved = 0;

  const ZSTD_matchState_t* const dms = ms->dictMatchState;
  const ZSTD_compressionParameters* const dictCParams = dictMode == ZSTD_dictMatchState ? &dms->cParams : NULL;
  const U32* const dictHashTable = dictMode == ZSTD_dictMatchState ? dms->hashTable : NULL;
  const U32 dictStartIndex = dictMode == ZSTD_dictMatchState ? dms->window.dictLimit : 0;
  const BYTE* const dictBase = dictMode == ZSTD_dictMatchState ? dms->window.base : NULL;
  const BYTE* const dictStart = dictMode == ZSTD_dictMatchState ? dictBase + dictStartIndex : NULL;
  const BYTE* const dictEnd = dictMode == ZSTD_dictMatchState ? dms->window.nextSrc : NULL;
  const U32 dictIndexDelta = dictMode == ZSTD_dictMatchState ? prefixStartIndex - (U32)(dictEnd - dictBase) : 0;
  const U32 dictAndPrefixLength = (U32)(ip - prefixStart + dictEnd - dictStart);
  const U32 dictHLog = dictMode == ZSTD_dictMatchState ? dictCParams->hashLog : hlog;

  assert(dictMode == ZSTD_noDict || dictMode == ZSTD_dictMatchState);

  /* otherwise, we would get index underflow when translating a dict index
   * into a local index */
  assert(dictMode != ZSTD_dictMatchState || prefixStartIndex >= (U32)(dictEnd - dictBase));

  /* init */
  ip += (dictAndPrefixLength == 0);
  if (dictMode == ZSTD_noDict) {
    U32 const maxRep = (U32)(ip - prefixStart);
    if (offset_2 > maxRep)
      offsetSaved = offset_2, offset_2 = 0;
    if (offset_1 > maxRep)
      offsetSaved = offset_1, offset_1 = 0;
  }
  if (dictMode == ZSTD_dictMatchState) {
    /* dictMatchState repCode checks don't currently handle repCode == 0
     * disabling. */
    assert(offset_1 <= dictAndPrefixLength);
    assert(offset_2 <= dictAndPrefixLength);
  }

  /* Main Search Loop */
  while (ip < ilimit) { /* < instead of <=, because repcode check at (ip+1) */
    size_t mLength;
    size_t const h = ZSTD_hashPtr(ip, hlog, mls);
    U32 const current = (U32)(ip - base);
    U32 const matchIndex = hashTable[h];
    const BYTE* match = base + matchIndex;
    const U32 repIndex = current + 1 - offset_1;
    const BYTE* repMatch = (dictMode == ZSTD_dictMatchState && repIndex < prefixStartIndex)
                               ? dictBase + (repIndex - dictIndexDelta)
                               : base + repIndex;
    hashTable[h] = current; /* update hash table */

    if ((dictMode == ZSTD_dictMatchState) &&
        ((U32)((prefixStartIndex - 1) - repIndex) >=
            3) /* intentional underflow : ensure repIndex isn't overlapping dict + prefix */
        && (MEM_read32(repMatch) == MEM_read32(ip + 1))) {
      const BYTE* const repMatchEnd = repIndex < prefixStartIndex ? dictEnd : iend;
      mLength = ZSTD_count_2segments(ip + 1 + 4, repMatch + 4, iend, repMatchEnd, prefixStart) + 4;
      ip++;
      ZSTD_storeSeq(seqStore, ip - anchor, anchor, 0, mLength - MINMATCH);
    } else if (dictMode == ZSTD_noDict && ((offset_1 > 0) & (MEM_read32(ip + 1 - offset_1) == MEM_read32(ip + 1)))) {
      mLength = ZSTD_count(ip + 1 + 4, ip + 1 + 4 - offset_1, iend) + 4;
      ip++;
      ZSTD_storeSeq(seqStore, ip - anchor, anchor, 0, mLength - MINMATCH);
    } else if ((matchIndex <= prefixStartIndex)) {
      if (dictMode == ZSTD_dictMatchState) {
        size_t const dictHash = ZSTD_hashPtr(ip, dictHLog, mls);
        U32 const dictMatchIndex = dictHashTable[dictHash];
        const BYTE* dictMatch = dictBase + dictMatchIndex;
        if (dictMatchIndex <= dictStartIndex || MEM_read32(dictMatch) != MEM_read32(ip)) {
          assert(stepSize >= 1);
          ip += ((ip - anchor) >> kSearchStrength) + stepSize;
          continue;
        } else {
          /* found a dict match */
          U32 const offset = (U32)(current - dictMatchIndex - dictIndexDelta);
          mLength = ZSTD_count_2segments(ip + 4, dictMatch + 4, iend, dictEnd, prefixStart) + 4;
          while (((ip > anchor) & (dictMatch > dictStart)) && (ip[-1] == dictMatch[-1])) {
            ip--;
            dictMatch--;
            mLength++;
          } /* catch up */
          offset_2 = offset_1;
          offset_1 = offset;
          ZSTD_storeSeq(seqStore, ip - anchor, anchor, offset + ZSTD_REP_MOVE, mLength - MINMATCH);
        }
      } else {
        assert(stepSize >= 1);
        ip += ((ip - anchor) >> kSearchStrength) + stepSize;
        continue;
      }
    } else if (MEM_read32(match) != MEM_read32(ip)) {
      /* it's not a match, and we're not going to check the dictionary */
      assert(stepSize >= 1);
      ip += ((ip - anchor) >> kSearchStrength) + stepSize;
      continue;
    } else {
      /* found a regular match */
      U32 const offset = (U32)(ip - match);
      mLength = ZSTD_count(ip + 4, match + 4, iend) + 4;
      while (((ip > anchor) & (match > prefixStart)) && (ip[-1] == match[-1])) {
        ip--;
        match--;
        mLength++;
      } /* catch up */
      offset_2 = offset_1;
      offset_1 = offset;
      ZSTD_storeSeq(seqStore, ip - anchor, anchor, offset + ZSTD_REP_MOVE, mLength - MINMATCH);
    }

    /* match found */
    ip += mLength;
    anchor = ip;

    if (ip <= ilimit) {
      /* Fill Table */
      assert(base + current + 2 > istart); /* check base overflow */
      hashTable[ZSTD_hashPtr(base + current + 2, hlog, mls)] =
          current + 2; /* here because current+2 could be > iend-8 */
      hashTable[ZSTD_hashPtr(ip - 2, hlog, mls)] = (U32)(ip - 2 - base);

      /* check immediate repcode */
      if (dictMode == ZSTD_dictMatchState) {
        while (ip <= ilimit) {
          U32 const current2 = (U32)(ip - base);
          U32 const repIndex2 = current2 - offset_2;
          const BYTE* repMatch2 =
              repIndex2 < prefixStartIndex ? dictBase - dictIndexDelta + repIndex2 : base + repIndex2;
          if (((U32)((prefixStartIndex - 1) - (U32)repIndex2) >= 3 /* intentional overflow */) &&
              (MEM_read32(repMatch2) == MEM_read32(ip))) {
            const BYTE* const repEnd2 = repIndex2 < prefixStartIndex ? dictEnd : iend;
            size_t const repLength2 = ZSTD_count_2segments(ip + 4, repMatch2 + 4, iend, repEnd2, prefixStart) + 4;
            U32 tmpOffset = offset_2;
            offset_2 = offset_1;
            offset_1 = tmpOffset; /* swap offset_2 <=> offset_1 */
            ZSTD_storeSeq(seqStore, 0, anchor, 0, repLength2 - MINMATCH);
            hashTable[ZSTD_hashPtr(ip, hlog, mls)] = current2;
            ip += repLength2;
            anchor = ip;
            continue;
          }
          break;
        }
      }

      if (dictMode == ZSTD_noDict) {
        while ((ip <= ilimit) && ((offset_2 > 0) & (MEM_read32(ip) == MEM_read32(ip - offset_2)))) {
          /* store sequence */
          size_t const rLength = ZSTD_count(ip + 4, ip + 4 - offset_2, iend) + 4;
          U32 const tmpOff = offset_2;
          offset_2 = offset_1;
          offset_1 = tmpOff; /* swap offset_2 <=> offset_1 */
          hashTable[ZSTD_hashPtr(ip, hlog, mls)] = (U32)(ip - base);
          ZSTD_storeSeq(seqStore, 0, anchor, 0, rLength - MINMATCH);
          ip += rLength;
          anchor = ip;
          continue; /* faster when present ... (?) */
        }
      }
    }
  }

  /* save reps for next block */
  rep[0] = offset_1 ? offset_1 : offsetSaved;
  rep[1] = offset_2 ? offset_2 : offsetSaved;

  /* Return the last literals size */
  return iend - anchor;
}

size_t ZSTD_compressBlock_fast(
    ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM], void const* src, size_t srcSize)
{
  ZSTD_compressionParameters const* cParams = &ms->cParams;
  U32 const mls = cParams->minMatch;
  assert(ms->dictMatchState == NULL);
  switch (mls) {
    default: /* includes case 3 */
    case 4:
      return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, 4, ZSTD_noDict);
    case 5:
      return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, 5, ZSTD_noDict);
    case 6:
      return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, 6, ZSTD_noDict);
    case 7:
      return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, 7, ZSTD_noDict);
  }
}

size_t ZSTD_compressBlock_fast_dictMatchState(
    ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM], void const* src, size_t srcSize)
{
  ZSTD_compressionParameters const* cParams = &ms->cParams;
  U32 const mls = cParams->minMatch;
  assert(ms->dictMatchState != NULL);
  switch (mls) {
    default: /* includes case 3 */
    case 4:
      return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, 4, ZSTD_dictMatchState);
    case 5:
      return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, 5, ZSTD_dictMatchState);
    case 6:
      return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, 6, ZSTD_dictMatchState);
    case 7:
      return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, 7, ZSTD_dictMatchState);
  }
}

static size_t ZSTD_compressBlock_fast_extDict_generic(
    ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM], void const* src, size_t srcSize, U32 const mls)
{
  const ZSTD_compressionParameters* const cParams = &ms->cParams;
  U32* const hashTable = ms->hashTable;
  U32 const hlog = cParams->hashLog;
  /* support stepSize of 0 */
  U32 const stepSize = cParams->targetLength + !(cParams->targetLength);
  const BYTE* const base = ms->window.base;
  const BYTE* const dictBase = ms->window.dictBase;
  const BYTE* const istart = (const BYTE*)src;
  const BYTE* ip = istart;
  const BYTE* anchor = istart;
  const U32 dictStartIndex = ms->window.lowLimit;
  const BYTE* const dictStart = dictBase + dictStartIndex;
  const U32 prefixStartIndex = ms->window.dictLimit;
  const BYTE* const prefixStart = base + prefixStartIndex;
  const BYTE* const dictEnd = dictBase + prefixStartIndex;
  const BYTE* const iend = istart + srcSize;
  const BYTE* const ilimit = iend - 8;
  U32 offset_1 = rep[0], offset_2 = rep[1];

  /* Search Loop */
  while (ip < ilimit) { /* < instead of <=, because (ip+1) */
    const size_t h = ZSTD_hashPtr(ip, hlog, mls);
    const U32 matchIndex = hashTable[h];
    const BYTE* const matchBase = matchIndex < prefixStartIndex ? dictBase : base;
    const BYTE* match = matchBase + matchIndex;
    const U32 current = (U32)(ip - base);
    const U32 repIndex = current + 1 - offset_1;
    const BYTE* const repBase = repIndex < prefixStartIndex ? dictBase : base;
    const BYTE* const repMatch = repBase + repIndex;
    size_t mLength;
    hashTable[h] = current;          /* update hash table */
    assert(offset_1 <= current + 1); /* check repIndex */

    if ((((U32)((prefixStartIndex - 1) - repIndex) >= 3) /* intentional underflow */ & (repIndex > dictStartIndex)) &&
        (MEM_read32(repMatch) == MEM_read32(ip + 1))) {
      const BYTE* repMatchEnd = repIndex < prefixStartIndex ? dictEnd : iend;
      mLength = ZSTD_count_2segments(ip + 1 + 4, repMatch + 4, iend, repMatchEnd, prefixStart) + 4;
      ip++;
      ZSTD_storeSeq(seqStore, ip - anchor, anchor, 0, mLength - MINMATCH);
    } else {
      if ((matchIndex < dictStartIndex) || (MEM_read32(match) != MEM_read32(ip))) {
        assert(stepSize >= 1);
        ip += ((ip - anchor) >> kSearchStrength) + stepSize;
        continue;
      }
      {
        const BYTE* matchEnd = matchIndex < prefixStartIndex ? dictEnd : iend;
        const BYTE* lowMatchPtr = matchIndex < prefixStartIndex ? dictStart : prefixStart;
        U32 offset;
        mLength = ZSTD_count_2segments(ip + 4, match + 4, iend, matchEnd, prefixStart) + 4;
        while (((ip > anchor) & (match > lowMatchPtr)) && (ip[-1] == match[-1])) {
          ip--;
          match--;
          mLength++;
        } /* catch up */
        offset = current - matchIndex;
        offset_2 = offset_1;
        offset_1 = offset;
        ZSTD_storeSeq(seqStore, ip - anchor, anchor, offset + ZSTD_REP_MOVE, mLength - MINMATCH);
      }
    }

    /* found a match : store it */
    ip += mLength;
    anchor = ip;

    if (ip <= ilimit) {
      /* Fill Table */
      hashTable[ZSTD_hashPtr(base + current + 2, hlog, mls)] = current + 2;
      hashTable[ZSTD_hashPtr(ip - 2, hlog, mls)] = (U32)(ip - 2 - base);
      /* check immediate repcode */
      while (ip <= ilimit) {
        U32 const current2 = (U32)(ip - base);
        U32 const repIndex2 = current2 - offset_2;
        const BYTE* repMatch2 = repIndex2 < prefixStartIndex ? dictBase + repIndex2 : base + repIndex2;
        if ((((U32)((prefixStartIndex - 1) - repIndex2) >= 3) & (repIndex2 > dictStartIndex)) /* intentional overflow */
            && (MEM_read32(repMatch2) == MEM_read32(ip))) {
          const BYTE* const repEnd2 = repIndex2 < prefixStartIndex ? dictEnd : iend;
          size_t const repLength2 = ZSTD_count_2segments(ip + 4, repMatch2 + 4, iend, repEnd2, prefixStart) + 4;
          U32 tmpOffset = offset_2;
          offset_2 = offset_1;
          offset_1 = tmpOffset; /* swap offset_2 <=> offset_1 */
          ZSTD_storeSeq(seqStore, 0, anchor, 0, repLength2 - MINMATCH);
          hashTable[ZSTD_hashPtr(ip, hlog, mls)] = current2;
          ip += repLength2;
          anchor = ip;
          continue;
        }
        break;
      }
    }
  }

  /* save reps for next block */
  rep[0] = offset_1;
  rep[1] = offset_2;

  /* Return the last literals size */
  return iend - anchor;
}

size_t ZSTD_compressBlock_fast_extDict(
    ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM], void const* src, size_t srcSize)
{
  ZSTD_compressionParameters const* cParams = &ms->cParams;
  U32 const mls = cParams->minMatch;
  switch (mls) {
    default: /* includes case 3 */
    case 4:
      return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, 4);
    case 5:
      return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, 5);
    case 6:
      return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, 6);
    case 7:
      return ZSTD_compressBlock_fast_extDict_generic(ms, seqStore, rep, src, srcSize, 7);
  }
}
